IS THE HEROINE mentally defective? Is the movie all supposed to be a dream? Questions like these plagued me on the way out of this year's great art-house success d'estime, Dancer in the Dark, by Lars von Trier.

The film won high awards at Cannes, both the Palme d'Or and the best actress honor for its star, Björk. Local theater managers, however, ought to label their exits "For Those Who Loved It" and "For Those Who Hated It." Members of the audience could find some consolation with like minds on the way out.

Even Entertainment Weekly had twin critics Lisa Schwarzbaum and Owen Gleiberman give differing reviews. She loved it; he disliked it, calling Dancer in the Dark "a crock, a very pretty, deftly executed crock." I can't even praise von Trier's skills as a potter--the film is too half-kilned.

Icelandic pop star Björk plays Selma, a dreamy single mom, a Czech immigrant living by the railroad tracks in a small town in Washington state in the early 1960s. Selma is a blemished mouse with bottle-bottom glasses who toils in a metal basin factory and threads hairpins onto cards for extra money at night. In the factory scenes, von Trier brings the sleepy, dim-visioned Selma ever closer and closer to a steel press; at times, Dancer in the Dark seems like an avant-garde industrial safety film.

Selma transcends her life of hard work at the movies. She loves musicals, which she attends with her friend Kathy (Catherine Deneuve). In times of stress and exhaustion, Selma imagines herself as a star, singing in the center of elaborate dance routines. At the same time, this wee, plain woman is also starring as Maria in the local little-theater production of The Sound of Music.

On top of all this, Selma is also losing her sight, through a genetic disease something like retinitis pigmentosa. Her son, Gene (Vladica Kostic), is afflicted as well and must have an operation by the time he is 13. Selma shares her secret loss of vision only with her landlord and good friend, Bill (David Morse), the town's constable. He, in turn, tells her a secret of his own: he's on the brink of suicide over his money problems.

One evening, Bill spies Selma's money for her son's operation, a metal candy box full of dollar bills. He steals her savings, starting a chain of events that ends in a serious court case for the frightened Selma. Selma furthers her troubles by refusing to tell of Bill's desperate money problems in court, because she's still keeping his secret.

Björk's Artful Noises: On 'Selmasongs,' the soundtrack to 'Dancer in the Dark,' Björk marries mechanical sounds to musical fantasies.

WHAT VON TRIER IS aiming at in Dancer in the Dark is hard to judge. Essentially, the film is violently erratic, just like so much of von Trier's work outside of Breaking the Waves, a film that now seems to have achieved its greatness not just because of the director but also because of photographer Robby Müller and the tender, desperate acting of Emily Watson.

It's well known that von Trier took a "vow of chastity," the Dogme 95 oath, which forbids the use of artificial lighting and sound, and melodramatic devices like guns. Thus von Trier and his fellow Dogme faithful seek to avoid violent, special-effects-ridden Hollywood-style cinema.

While the Dogme school has been a welcome experiment, all the Dogme films released here have depended on sensational, melodramatic topics--such as miscarriage (julien donkey-boy), incest (The Celebration) and prostitution (Mifune).

Dancer in the Dark is released without the Dogme certificate of approval. It's filmed in wide-screen format, and the use of a clip from the 1933 film 42nd Street must violate the commandment against artifical lighting somehow. Still, the aesthetics of Dancer in the Dark are almost completely Dogme-atic, in the dim colorless color and in the cold, canned-looking digitally filmed dream sequences that make up about a quarter of the film's running time.

Outré as they are, Selma's dream-musical sequences aren't a visual relief from the film's dedicated realism--a realism that the unlikely plot defies. The misfortunes that befall Selma are ancient silent-movie plot devices, contrasted with the improbability of standard musical-comedy motifs.

Selma may believe that she's like the characters in the musicals she loves, that everything will turn out right for her in the end. She has a fantasy father--Novy, a musical-comedy star from Czechoslovakia who went to Hollywood for a minor career. We never see what Novy's movies looked like, but he's played in old age by Joel Grey.

And when Selma is denied by Novy in court, we know that scant hope remains for her. Cinema itself has orphaned Selma. It's a dour way of looking at the musicals, but it fits with von Trier's view of the movies as an exacting discipline, with techniques that must be renounced in order to grasp the purity of filmmaking.

I'd trade all of Dancer in the Dark for the ending of von Trier's 1998 movie, The Idiots. In the last scene of The Idiots, we see the return home of Karen (Bodil Jorgensen), who ran away from her husband after a terrible domestic tragedy. She's sitting and eating in her living room with her husband's pious, hard Danish relatives, who are bathing the strayed wife in their silent scorn.

Trembling with tension, Karen decides to make an infantile joke of spitting out her dinner, and her husband slaps her. Von Trier keeps the camera on Jorgensen: the chewed food still on her lips, the sudden pain in her eyes.

But this forceful scene was the finale of a rambling, careless film. That slapped face shocked the breath out of me because it was a surprise. When von Trier wallops Selma, the slap descends on the woman in slow motion and lasts the entire second half of the movie.

The justifications for Selma's ordeal are, when studied, nonsense. Von Trier's jump cuts, his elisions, can't quite disguise the preposterousness of Dancer in the Dark, although he obscures the places where the unlikely scenes would be. We don't see Kathy retrieving Selma's money from an eye doctor (played by Udo Kier--it can't be easy getting money out of this eye doctor, who looks as if he'd steal your corneas).

Later, von Trier's unfamiliarity with the U.S. judicial system left me incredulous. The average moviegoer visits death row more often than Sister Prejean does; unlike von Trier, the viewer knows about the existence of the pro-bono law case. If tears do not blind you, you might feel the director has some explaining to do.

AS USUAL, von Trier gets enormous aid from his actors. As the weak, thieving landlord, Morse has enough gravity to hold up the tower of improbabilities that make up his part, just as he made the improbability of The Green Mile work. Siobhan Fallon does a similar trick in gently underplaying a prison warden.

As for Björk--you can praise her simplicity, but she's better off arty. Dancer in the Dark is most interesting when von Trier leaves Björk to be Björk. The musical interludes are modeled on the way a classic musical erupts into song. But the songs here aren't "Doe, a Deer," they're typical dissonant Björkery: ballet mecaniques of squawks, yips and slams, vocal throbs and mutters.

Björk does the Björk dance: that pirouette and collapse into a fetal position, hands laid palm-flat on her wry, faintly smiling face. She's a sinister Arctic pixie escaped from some uncanny Christmas card. Call it Björk's Law: the scariest women are the shortest ones.

In the fantasy sequence of the police coming for Selma, Björk gives Dancer in the Dark a thrill of horror. As she glides around, dancing with a cadaver, she's as winsomely macabre as a garden gnome. Björk's Little Blind Match Girl act, however, is unlikely, since we see what a presence the singer possesses. When Selma is finally driven to violence, that violence is against her will. After all she's endured doesn't she have any rage? How did this Selma ever rally herself to cross the Iron Curtain? While Björk is much weirder than Madonna, she's just as solidly posed, and so thoroughly a diva, that even her disguise can't conceal her. And the movie is only really compelling when she sheds that mousy skin in the few musical sequences.

DANCER IN THE DARK (the title might be a sick joke about Selma's fate) may hit the alternative-film audiences where they live. Under their veneer of sophistication, they mourn for the potency and populism of old movies. Cool crowds are starting to turn up in London and L.A. at screenings of The Sound of Music to sing along in costume. (They used to turn up at The Rocky Horror Picture Show, a celebration of polysexuality; now they're buying tickets to camp it up at the most sexless movie of all time.)

Dancer in the Dark fixes the musical-watching experience with the same comforting level of distance that drag queens use to excuse themselves for singing "(How Do You Solve a Problem Like) Maria?" This new von Trier film gives audiences permission to revel in old-movie tragedy and Rodgers and Hammerstien references alike, by presenting them both tricked out with jaggedy, rickety cutting, hand-held camerawork and Björk's eerieness.

Some may think that Dancer in the Dark is hard-hitting, that the film exposes the gap between the promises of eternal happiness that the musicals offered and the bitter reality of the viewer's lives. Even this exposé is a kind of crock, now. By bringing pleasure to varied audiences from yesterday's families to today's ironists, these classic musicals have fulfilled something of their promises of endlessness, of eternity.

Many an erstwhile realistic melodrama has aged far worse than an escapist bonbon like 42nd Street. An audience longing for the music and simplicity of the old movies isn't the same thing as an audience longing for the stupidity of a bad old-movie plot.

I realize that a new, great film released today will automatically seem like an oddity. In contrast, Dancer in the Dark will seem like a great film, but it's only a great oddity.

Dancer in the Dark (R; 140 min.), directed and written by Lars von Trier, photographed by Robby Müller and starring Björk, David Morse and Catherine Deneuve, opens at Camera One in San Jose and at the Park in Menlo Park.